feat: 新增文件上传服务

- 添加 UploadHandler 处理文件上传
- 添加 UploadService 实现文件存储
- 配置上传文件大小限制和存储路径

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/internal/handler/upload_handler.go

@@ -0,0 +1,60 @@
+package handler
+
+import (
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+	"x-agents/server/internal/service"
+)
+
+type UploadHandler struct {
+	uploadService *service.UploadService
+}
+
+func NewUploadHandler(uploadService *service.UploadService) *UploadHandler {
+	return &UploadHandler{uploadService: uploadService}
+}
+
+// Upload 上传文件
+func (h *UploadHandler) Upload(c *gin.Context) {
+	file, err := c.FormFile("file")
+	if err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"success": false, "message": "No file uploaded"})
+		return
+	}
+
+	// 检查文件大小（最大 100MB）
+	if file.Size > 100*1024*1024 {
+		c.JSON(http.StatusBadRequest, gin.H{"success": false, "message": "File too large (max 100MB)"})
+		return
+	}
+
+	result, err := h.uploadService.Upload(file)
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": err.Error()})
+		return
+	}
+
+	if !result.Success {
+		c.JSON(http.StatusInternalServerError, result)
+		return
+	}
+
+	c.JSON(http.StatusOK, result)
+}
+
+// Delete 删除文件
+func (h *UploadHandler) Delete(c *gin.Context) {
+	filename := c.Param("filename")
+	if filename == "" {
+		c.JSON(http.StatusBadRequest, gin.H{"success": false, "message": "Filename is required"})
+		return
+	}
+
+	if err := h.uploadService.DeleteFile(filename); err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": err.Error()})
+		return
+	}
+
+	c.JSON(http.StatusOK, gin.H{"success": true, "message": "File deleted"})
+}